1. Field of the Invention
The present invention relates to a cyclone, an apparatus for separating slurry having the cyclone, and a system and a method of supplying slurry using the apparatus. More particularly, the present invention relates to a cyclone for rotating slurry, an apparatus for separating the slurry by sizes using the cyclone, and a system and a method of supplying the separated slurry to a polishing apparatus using the apparatus.
2. Description of the Related Art
Modern semiconductor devices are typically formed of multiple layers of wiring structures formed by sandwiched conductive and insulation layers that have been etched to make the desire circuit patterns. Planarization is an important component of this process. Examples of planarization processes used include an etch-back process, a reflow process, a chemical mechanical polishing (CMP) process, etc.
The CMP process was originally developed by IBM Corporation in U.S. in late 1980s. In a typical CMP process, a slurry including deionized water, an abrasive, an additive, etc., is provided between a polishing pad and the semiconductor substrate. The semiconductor substrate and the polishing pad are then rotated in reverse directions to polish a surface of the semiconductor substrate. That is, a plurality of minute surface projections of the abrasive and the polishing pad is rubbed against the surface of the semiconductor substrate to mechanically polish the surface of the semiconductor substrate. Simultaneously, chemical components in the slurry are chemically reacted with the surface of the semiconductor substrate to chemically polish the surface of the semiconductor substrate.
The efficacy of the polishing process is due in great part to the composition of the slurry used. A main drawback to using such slurries is that particle size changes over time due to agglomeration mechanisms between micro-particles within the slurry. The result is the unwanted formation of macro-particles by chemical bonding of resulting hydrophobic siloxane groups.
To address the macro-particle formation problem, such particles are precipitated out of the slurry before use and scrapped. This is generally wasteful of the expensive slurry material and increases the cost for manufacturing a semiconductor device.
Alternate methods have been proposed for providing the slurry without the macro-particles. In one such system, a separator within the reproducing unit separates the slurry by sizes. A supersonic pulverizer then pulverizes particles having a size larger than a predetermined size and the pulverized particles again separated. A mixing unit then mixes the separated slurry and deionized water and the slurry having the applicable concentration is then supplied to the CMP apparatus.
A conventional apparatus for separating slurry by particle size/specific gravity includes a housing containing a cyclone. The cyclone has an inlet passageway through which the slurry is introduced, and a cylindrical passageway and a conical passageway in which the slurry is rotated. A drawback to this system is that such conventional cyclones are known to be relatively inefficient at separating the slurry particles.
A further drawback is the spaced arrangement between the apparatus separating the particles of the slurry and the unit mixing the particles back into the slurry. Such spacing requires the separated slurry to be transported in a container between the two stations. While being transported, however, the above-mentioned agglomeration mechanism causes macro-particles to again be formed within the container.
Accordingly, the need remains for a cyclone with improved separating efficiency as well as a system that integrally separates the slurry and mixing the slurry with deionized water.